The inventive concept relates generally to electronic data storage technologies. More particularly, the inventive concept relates to methods and apparatuses for generating program data for nonvolatile memory devices.
Flash memory is a type of electrically erasable programmable read only memory (EEPROM) that has gained increasing popularity in recent years due to attractive features such as relatively low cost, efficient performance, low power consumption, and nonvolatile data storage. In an effort to further improve flash memory, researchers have continually sought ways to increase its data storage capacity, reliability, durability, and various other parameters.
One way to increase the storage capacity of flash memory is by storing more than one bit of data per memory cell. A flash memory capable of storing more than one bit of data is referred to as a multi-level-cell (MLC) flash memory. Unfortunately, increasing the number of bits stored in each memory cell tends to reduce the reliability of stored data. One reason for this decrease in reliability is that increasing the number of bits tends to decrease the margins between threshold voltage distributions representing the stored data. This reduction in margins may lead to overlapping distributions, making it difficult or impossible to distinguish between different data states. Moreover, the problem of reduced margins is exacerbated by electrical effects that can widen the threshold voltage distributions of programmed memory cells, such as coupling between adjacent memory cells.
In view of these and other shortcomings, there is a general need for techniques and technologies to improve the reliability of flash memory devices, especially those designed to store more than one bit of data per memory cell.